Identification—
Mix a portion of finely powdered Tablets,equivalent to about 1g of methocarbamol,with 25mLof water in a separator,and extract with 25mLof chloroform.Filter the extract,and evaporate to dryness:the residue of methocarbamol so obtained responds to
Identificationtest
Aunder
Methocarbamol.
Dissolution,Procedure for a Pooled Sample á711ñ—
Medium:
water;900mL.
Apparatus 2:
50rpm.
Time:
45minutes.
Procedure—
Determine the amount of C
11H
15NO
5dissolved,employing the procedure set forth in the
Assay,making any necessary modifications.
Tolerances—
Not less than 75%(Q)of the labeled amount of C11H15NO5is dissolved in 45minutes.
Assay—
pH4.5Buffer solution,Mobile phase,andChromatographic system—
Proceed as directed in the
Assayunder
Methocarbamol Injection.
Internal standard solution—
Prepare a solution of caffeine in methanol containing about 3mg per mL.
Standard preparation—
Transfer about 100mg of
USP Methocarbamol RS,accurately weighed,to a 100-mLvolumetric flask.Dissolve in about 50mLof
pH4.5Buffer solutionand 25mLof methanol.Add 5.0mLof
Internal standard solution,dilute with
pH4.5Buffer solutionto volume,and mix.
Assay preparation—
Weigh and powder not less than 10Tablets.Transfer an accurately weighed portion of the powder,equivalent to 100mg of methocarbamol,to a 100-mLvolumetric flask.Add about 50mLof pH4.5Buffer solution,25mLof methanol,and 5.0mLof Internal standard solution.Shake vigorously for 10minutes,dilute with pH4.5Buffer solutionto volume,and mix.Filter,discarding the first 20mLof the filtrate.
Procedure—
Proceed as directed for
Procedurein the
Assayunder
Methocarbamol Injection.Calculate the quantity,in mg,of methocarbamol (C
11H
15NO
5)in the portion of Tablets taken by the formula:
100C(RU/RS),
in which
Cis the concentration,in mg per mL,of
USP Methocarbamol RSin the
Standard preparation;and
RUand
RSare the peak response ratios of methocarbamol and caffeine obtained from the
Assay preparationand the
Standard preparation,respectively.